Radio communication technology has traditionally been based upon fixed frequency or spectrum assignments and fixed modulation techniques (as well as other regulatory agency established parameters). For example, a particular local government agency such as a police department might be assigned several frequencies for its use using frequency modulation for voice communication. Frequency spectrum could often be shared amongst groups of users in order to more efficiently use the spectrum by, for example, sub-audible digital or analog coding embedded in the transmitted signals. Nevertheless, in such an environment, the assigned frequencies are off limits for use by others and usage would rarely approach full utilization. In fact, utilization might amount to only a few percent of the available communication throughput. As a result, frequency spectrum is inefficiently utilized, while simultaneously demand for bandwidth is ever increasing.
A new paradigm for dealing with such a problem is emerging in which a radio is provided with the intelligence to identify underutilized or unutilized spectrum and change its operational parameters to take advantage of the available spectrum while minimizing potential for causing interference. Such radios are commonly configurable and reconfigurable using software control and posses the intelligence to obtain the needed situational awareness to reconfigure in order to enhance spectrum utilization efficiency. Such radios have been dubbed cognitive radios—a form of software defined radio. Cognitive radios are envisioned to be able to cross geographic boundaries and adapt to regulatory changes associated therewith.
One issue that is to be addressed in producing a viable working cognitive radio is the issue of adaptation to new policies as a radio's situation or environment changes. This can happen, for example, by virtue of changes in a geographically static environment as well as changes resulting from geographical movement of the radio (e.g., in an automobile or an airplane). The cognitive radio should be able to competently adapt to such situations
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